Impact of ~(18)F-FDG PET/CT on the Clinical Restaging and Therapeutic Regimens in Post-Treatment Patients with Gastric Carcinoma

Objective To investigate the value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography(18F-FDG PET/CT) in the follow-up of post-treatment patients with gastric cancer and to investigate the impact of 18F-FDG PET/CT on the clinical restaging and therapeutic regimens.Methods A retrospective study was conducted in 55 post-treatment patients with gastric cancer.18F-FDG PET/CT scan was performed at 60 min(early phase) and 120 min(delayed phase) after 18F-FDG administration.18F-FDG PET/CT of delayed phase was undertaken after gastric filling with moderate water.If necessary,enhanced CT was also performed.The value of 18F-FDG PET/CT in the follow-up of post-treatment patients with gastric cancer was evaluated based on recurrence,lymph node metastases and lymph node external metastases respectively,and it was compared with CT.Meanwhile,the impact of 18F-FDG PET/CT on the restaging and treatment decision was also analyzed in this study.Additionally,the maximum of standardized uptake value(SUVmax) of early and delayed phases in the anastomotic stoma was measured,and the percentage change of SUVmax(△SUVmax%) was also calculated in this study.Tumor recurrence and/or metastases were finally confirmed by pathology.Data was analyzed with SAS 9.13.Results(1) The accuracy of 18F-FDG PET/CT in the diagnosis of gastric recurrence was 96.4%(53/55),which was significantly higher than CT(85.5%).In the detection of lymph node metastases,the sensitivity,accuracy and negative predictive value(NPV) of 18F-FDG PET/CT(92.0%,96.4% and 93.8%) showed statistically significant differences compared with CT(60.0%,81.8% and 75.0%).In addition,the sensitivity and accuracy of 18F-FDG PET/CT in detecting lymph node external metastases were 81.8% and 90.9%,significantly higher than CT(45.5%,76.4%).(2)18F-FDG PET/CT changed the TNM stage in 34.5%(19/55) cases,and the therapeutic strategies of 21.8%(12/55) cases were changed due to PET/CT findings.(3)△SUVmax% was(22.8±9.8)% and(8.6±13.3)% in gastric recurrence and the anastomotic inflammation with statistically significant differences between the two groups(P0.05).Conclusion 18F-FDG PET/CT is a superior post-operative surveillance modality in the diagnosis of recurrence and metastases in post-treatment patients with gastric cancer compared with CT.18F-FDG PET/CT has great impact on the clinical restaging and proper re-treatment regimens.18F-FDG PET/CT of delayed phase after gastric filling with water may be one of the best ways in discriminating the recurrence from the inflammation in anastomotic stoma.